There are many many reasons why this should be done. Firstly. Number 1 rule is never assume anything. Until you measure and check something, you dont know. That is why you measure and check things. This should apply to every aspect of an engine assembly. It is better to check everything and find nothing wrong, than to not check something and have it fuck your shit right up. A piston to valve contact, even minor, can cause the valve to weaken and then snap and drop into the combustion chmaber. This is catastrophic and will fuck the heads, piston, and the block instantly. It will basically turn the entire motor into scrap metal faster than the blink of an eye. Relating to why cams should be degree'd and aswell as check piston to deck hieght. Valve clearnces etc. Firstly, engines being rebuilt will have the block deck surface / cylinder head surfaces cut. As much as 0.010" per cut. And sometimes engines are built more than once. So this can add up. And it is often never known how much has been taken off by the engine machinest or previous freshen ups. It can be addressed with thicker head gaskets. But again, you have no way of knowing unless you measure things. This different hieght will change the timing between crank and cam because the distance between the 2 has changed, but the belt/chain is a set length with set timing posistions. Resulting in the cams being out of phase. (Only a very small amount, but these errors stack up.) Another thing that could affect things is if the cylinder head has had new valves, or new valve seats cut in. This can change the installed hieght of the valve and therefore how far into the combustion chamber it protudes. Also oversize valves can be used aswell which have larger diameters at the head, which throws things out aswell. Different cam profiles, especially performance cams will have more lift and more duration. And differing amounts of valve overlap. Variable cams (depending on which motor) will change the cam phasing. And are often driven by oil pressure and only controlled after the fact. That is, only adjusted by the ecu after a difference (error) between target and measured cam position is noticed. Different piston designs will have different dish and valve reliefs. Another thing that causes the cam phasing to be inaccurate Is that the cam shaft where the cam sprockets connects is very small diameter. Therefore any locating pins/dowels must be very close to center of rotation. That means that any small clearance between the dowel and the counterbore it slots into can result in a significant variation of rotational degrees from where its meant to be. (It must be clearanced to allow it to fit) On standard engines none of this is much of an issue. On modified engines with large lift/duration cams, different piston dish designs/valve relief, oversize valves, decked mating surfaces, different thickness head gaskets or any number of variables. It can be disastrous. Reading the comments and i can see a number of retards have said this is not needed or not possible. Which clearly demonstrates a total lack of understanding.
Also not to mention valve float at high rpm. Or exhasut valves literally being blown open because of aggressive anti lag stategies causing violent explosions in the exhaust. Or timing belt stretch / timing chain wear with age.
If an engine is set up that "tightly" where there is almost 0 room for error, then the tiniest amount of accidental valve float would instantly turn that engine into a blender. The solution would be to go slightly smaller on the camshafts (less duration and/or lift), deeper valve reliefs on the piston (would reduce compression ratio). I'd rather have slightly less aggressive parts with more wiggle room than to have an engine setup so tightly that even a fraction of a slip by the adjustable cam gear because of bolts not tightened enough caused a piston to obliterate a valve. The only thing degreeing a cam or cams should be used for is to double check for poorly manufactured parts, which is very rare with today's manufacturing process and machinery used to do so.
Seems like scary shit. I hope my Aussie engine builder got this bit right for my LS3 Forged Stroked 416ci? Especially with a rev limit and engine cut-out set at 7,500rpm. Piston Travel Speed would be high...
@@Ed-qu8nz not always. Cam timing also plays a part in which you might need a different piston entirely(since in some cases you can't fly cut the piston enough)
but that would only be an issue if you somehow mis aligned the marks and had one cam or both just off. As long as you have all the marks for each cam lining up perfectly and according to spec there should absolutely be no problem. however if you're going with some serious duration increase in your cams then you need to look at the manufacturers requirements. Personally i have upgraded cams for my supra. and all you have to do is follow the factory install via the toyota oem workshop manual. I feel like degreeing cams is more necessary if you're having some custom camshaft made and need to make sure it is what they claim it is. but now days with how good machine quality is its consistent and not usually a problem.
In the video they state it's an aftermarket cam and looks like an aftermarket domed piston as well, they also state the cams are set to 0. The Skunk2 Pro 3's they're using in this video are some the most aggressive cams on the market for this engine, and it's really only these cams with these pistons that cause an issue (and anything similar or even more aggressive than this setup)
its not true sadly, firstly the manufacturer cant take into account any difference in tolerance between the head / block being machined. even a couple of thou could put the cams to crank relationship our by a degree or so. the only time its acceptable to just slap a set of cams in and time it up to the OEM marks, is with OEM cams and gears. ideally any aftermarket cam should be dialled in to the spec sheet provided, thats why they provide it, and check the p2v and v2v. Ive just done exactly this, dialled in aftermarket cams, to the spec on the paper, and had very little v2v clearance in my application, its just a common misconception that you can drop them in an go, because people are lucky enough to get away with it.
When they manufacturer those pulleys they have no idea how they will be used, or what the aftermarket camshaft manufacture will require, so the only logical thing they can do is mark the 0 on the cam gear to be the same as OEM 0 degrees. This means when you build the engine for the first time, you can at least time the engine up to how the manufacturer would have timed it. your not going be to teeth out at this point. Example, I just dialed in a set of Skunk2 tuner2 cams. With them set to the Cam Card, my intake was 1 mark (2 degrees) advanced, and -2 marks (4 degrees)Retarded on the exhaust. This is where the camshaft manufacturer expects the cam to be best, as a general rule of thumb, However, even with the above said, my V2V clearance was very tight as the recommended spec, so I had to move them slightly from there.
Wouldn’t this be why you need to set base engine mechanical timing, and “Degreeing” a camshaft be more in fine tuning mechanical timing? Just my understanding
What do you mean set base mechanical timing? The purpose of degreeing is so that the crank to cam phasing is aligned when some aftermarket cams and pistons are used
Makes no sense at all! You degree a cam to check the specs match the card and your timing will be on. Nothing to do with clearance! Piston to valve clearance is a measurement on peak lift. I’d never take an engine to you how you don’t know this is beyond me! You shouldn’t be doing work for ppl at all.
Rippee42 This video illustrates that the pistons hit the valves before peak lift, and if you degreed the cams to match the cam card, you would have significant interference. The point is to show how early in the cycle interference may happen so people can know what to expect. The pistons are pretty large dome, more than 13cc.
well, its like gambling, if you choose a longer duration camshaft for your vehicle. especially the nice long durations that give drag cars their nasty lope. then you have a much greater chance of bending a valve and ruining a valve guide, and potentially a piston and camshaft, that you just purchased. so for the sanity and sane factor i would degree everycamshaft that is greater than factory specs. there is alot of thoughts that camshafts are perfectly replicated everytime. thats where youd be wrong. we're talking degrees of of angle kinda precision. so ill leave it up to you. you could be lucky and not have to worry about it. but there can always be the possibility of ruining your motor so you choose.
this video is pointless you have high compression pistons with unknown rods and you are rotaing in the wrong direction. i would not trust you building a motor
Do you realy have to degree your cams? Im gaving alot of touble understanding this concept. Why cant you just line up the chain links with the timing marks on the crankshaft sprocket and the camshaft sprocket.
Andres Some radical cams are designed to be advanced or retarded and a high lift may hit the piston. A couple degrees can prevent this. Stock motors ? Dont worry about it.
If you're using flat top pistons you will probably never have an issue with piston/valve interference. If you have a high lift cam and/or big piston domes then you would want to check for interference. Even a slight dome and a high lift cam will almost never have any issues.
Pointless video. The Timing Belt Tensioner can only correctly tension the belt while the engine is rotating in the forward direction. It simply is not designed to work in opposite rotation; as evidenced by the piston/valve interference.
